Answer
$I = 10^{-7}~W/m^2$
Work Step by Step
We can find the final sound intensity:
$\beta = (10~dB)~log(\frac{I}{I_0})$
$50~dB = (10~dB)~log(\frac{I}{I_0})$
$5 = log(\frac{I}{I_0})$
$10^5 = \frac{I}{I_0}$
$I = I_0 \cdot~10^5$
$I = (10^{-12}~W/m^2)~(10^5)$
$I = 10^{-7}~W/m^2$
